The modification of membrane components, mainly proteins that occur in cells transformed by a temperature-sensitive mutant of Rous sarcoma virus are studied in order to ascertain the role of such modification in alterations of cell properties that are expressed at or mediated by the cell surface. Analysis of the role of specific cell surface polypeptide present in somatic cell hybrids in the expression of some normal cellular properties. Cell membranes are isolated and their composition determined by electrophoretic and chromatographic procedures. Membrane surface properties are investigated by the use of lectins and labeling with surface-selective techniques. Relations between different polypeptides in somatic cell hybrids are investigated by peptide mapping. BIBLIOGRAPHIC REFERENCES: Marcinani, D.J. and Okazaki, T.: Interaction of Con A with chick embryo fibroblast transformed by Rous sarcoma virus. Biochim. Biophys. Acta 455: 849-864, 1976. Papas, T.S., Pry, T.W. and Marciani, D.J.: Inactivation of avian myeloblastosis virus DNA polymerase by specific binding of pyridoxal 5'-phosphate to triphosphate binding site. J. Biol. Chem. 253: 1426-1430, 1977.